1. Technical Field
The present invention relates to an organic light emitting device and an electronic apparatus.
2. Related Art
An organic electroluminescence element (organic EL element) is configured to have an anode, a cathode, and a functional layer containing an organic light emitting layer interposed between the electrodes. The functional layer emits fluorescence or phosphorescence through conversion of energy, which is produced in the organic light emitting layer by recombination of holes injected from the anode and electrons injected from the cathode.
However, when moisture, oxygen, and the like enter the functional layer through the anode or the cathode from the outside, the injection of carriers (holes and electrons) into the organic light emitting layer is suppressed, so that the luminance of light emission decreases or the functional layer deteriorates, and thus the light emission function itself is lost, which leads to the formation of non-light emitting areas called dark spots.
In an organic EL device (organic light emitting device) having such an organic EL element (organic light emitting element), sealing layers covering the organic EL element are formed to prevent moisture, oxygen, and the like from entering.
As the sealing layer, in JP-A-2006-147528, for example, a cathode protection layer containing an inorganic material, such as silicon oxynitride, a buffer layer (planarization layer) containing a resin material, such as epoxy resin, and a gas barrier layer containing an inorganic material, such as silicon oxynitride, are formed into a multilayer body having a three-layer structure in which these layers are stacked in this order from a cathode side.
In an organic EL device having the sealing layer of such a structure, both the cathode protection layer and the gas barrier layer contain inorganic materials, such as silicon oxynitride, and therefore not only the gas barrier layer but also the cathode protection layer sometimes exhibits gas barrier properties of preventing entry of moisture, oxygen, and the like as in the case of the gas barrier layer.
Therefore, when the cathode protection layer also exhibits the gas barrier properties, the two layers of the cathode protection layer and the gas barrier layer have the gas barrier properties in the sealing layer. Accordingly, the sealing layer exhibits excellent gas barrier properties as compared with a case where one gas barrier layer forms the sealing layer, for example.
Thus, when both the cathode protection layer and the gas barrier layer are caused to exhibit the gas barrier properties, it is considered that the generation of the dark spots is apparently prevented in the organic EL element, and thus the life characteristics of the organic EL device are improved.
However, in the cathode protection layer and the gas barrier layer of the above-described structure, there is a certain probability of a defective portion, in which the gas barrier properties locally decrease resulting from the mixing of foreign substances into the layers or a defect arising in the structure in the layers, being generated.
Then, in a case where the sealing layer is, for example, a single layer of gas barrier layer, when such a defective portion is generated in the gas barrier layer (sealing layer), moisture, oxygen, and the like immediately enter the functional layer from the defective portion, and, as a result, dark spots are generated. Therefore, the generation of dark spots is detected as an initial failure, so that a problem regarding the reliability of the organic light emitting device, that is, dark spots being generated during use after the organic light emitting device has been shipped, does not arise.
On the other hand, it is supposed that such defective portions are generated in both of the two layers of the sealing layer, namely, the cathode protection layer and the gas barrier layer having the gas barrier properties (in particular, it is supposed that such defective portions are generated at separate positions when viewed in plan). It takes a certain period of time for moisture, oxygen, and the like to enter the functional layer through the two defective portions. Therefore, the generation of dark spots is not detected as an initial failure, which has caused a problem in that dark spots are generated during use by a purchaser after the organic EL device has been shipped, and as a result, the reliability of the organic EL device decreases.
Accordingly, in the organic light emitting device having the sealing layer composed of two layers, that is, the cathode protection layer and the gas barrier layer with gas barrier properties, the manufacturing yield is improved but dark spots are generated at a relatively early stage after shipment, which has caused a problem in that the organic EL device is not sufficiently reliable during use.